The idea is to use a laser to define the traces on a standard photoresist-covered PCB-laminate.

+

+

On way would be to use a UV-laser (with suitable wavelength) to expose a positive photoresist, and then develop and etch the board the usual way. An option to a laser might be to use a high powered UV-diode with focusing optics to make a small enough dot of light to be useful.

Ultraviolet light (UV) is non-ionizing radiation in the 180 to 400-nanometer wavelength region of the electromagnetic spectrum. The ultraviolet spectrum is commonly divided into the following three regions:

+

+

* UVA Black Light 315nm .. 400nm

+

* UVB Erythemal 280nm .. 314nm

+

* UVC Germicidal 180nm .. 280nm

+

+

Exposure to ultraviolet radiation is typically limited to the UVA region resulting from exposure to direct sunlight. The Earth’s atmosphere shields us from the more harmful UVC and greater than 99% of UVB radiation. However, some equipment can generate concentrated UV radiation in all the spectral regions that, if used without the appropriate shielding and personal protective equipment, can cause injury with only a few seconds of exposure.

+

+

==== EXPOSURE TO ULTRAVIOLET LIGHT ====

+

+

An unfortunate property of UV radiation is that there are no immediate warning symptoms to indicate overexposure. Symptoms of overexposure including varying degrees of erythema (sunburn) or photokeratitis (welder’s flash) typically appear hours after exposure has occurred.

+

+

* Skin Injury - UV radiation can initiate a photochemical reaction called erythema within exposed skin. This “sunburn” can be quite severe and can occur as a result of only a few seconds exposure. Effects are exaggerated for skin photosensitized by agents such as coal tar products, certain foods (e.g., celery root), certain medications and photoallergens. Chronic skin exposure to UV radiation has been linked to premature skin aging, wrinkles and skin cancer.

+

* Eye Injury – UV radiation exposure can injure the cornea, the outer protective coating of the eye. Photokeratitis is a painful inflammation of the eye caused by UV radiation-induced lesions on the cornea. Symptoms include a sensation of sand in the eye that may last up to two days. Chronic exposures to acute high-energy UV radiation can lead to the formation of cataracts.

+

+

==== SPECIAL WORK PRACTICES ====

+

+

* first rule: never allow the skin or eyes to be exposed to UV radiation sources. The UV radiation generated by laser equipment can exceed

+

recommended exposure limits and cause injury with exposures as brief as three seconds in duration.

+

* second rule to avoid Eye Injury: use protection glass, these are essential when operating a Class IV or Class IIIb laser in an environment where reflections can occur. They absorbs wavelengths from 370nm to 560nm, with an OD of +5 to +6 depending on the wavelength, unfortunately these will not provide protection against red or infrared lasers. They are intended for use with green, blue, and violet lasers.

+

+

+

[[File:laser-exposer-uv-laser-protetion-glass.jpg]]

+

+

+

405nm laser should be the safer choice

=== polygon mirror ===

=== polygon mirror ===

Line 28:

Line 84:

[[File:pcb-laser-exposer-idea.gif]]

[[File:pcb-laser-exposer-idea.gif]]

+

+

+

== operating with pulse laser circuit ==

+

+

* [http://www.jensign.com/opto/ledlaserdrivers article]

== beam idea from Panasonic KX P4410 ==

== beam idea from Panasonic KX P4410 ==

Line 67:

Line 128:

HU+ |13 24| OSCV

HU+ |13 24| OSCV

HU- |14 23| OSCC

HU- |14 23| OSCC

−

HV+ |15 22| FG-

+

HV+ |15 22| FG- <----- it may be interesting

−

HV- |16 21| FG+

+

HV- |16 21| FG+ <----- it may be interesting

HW+ |17 20| Amp.out

HW+ |17 20| Amp.out

HW- |18 19| FGout

HW- |18 19| FGout

Line 104:

Line 165:

19 FGout FG comparator output

19 FGout FG comparator output

20 Amp.out FG amp. output

20 Amp.out FG amp. output

−

21 FG+ FG signal input (+)

+

21 FG+ FG signal input (+)

22 FG- FG signal input (-)

22 FG- FG signal input (-)

23 OSCC OFF Timer setup -1

23 OSCC OFF Timer setup -1

Line 118:

Line 179:

36 N.C. N.C

36 N.C. N.C

+

+

+

+

cable M63154AFP

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|1 |- 4,5, 8,9,10,11 (gnd)

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|2 |- 31 (/dec, deceleration input)

+

|3 |- 32 (/acc, acceleration input)

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|4 |- 1,2 (Vcc)

</pre>

</pre>

Latest revision as of 12:27, 31 October 2014

For more interesting projects done by Flameman and Legacy, be sure to check out his project index

pcb laser exposer

project idea

The idea is to use a laser to define the traces on a standard photoresist-covered PCB-laminate.

On way would be to use a UV-laser (with suitable wavelength) to expose a positive photoresist, and then develop and etch the board the usual way. An option to a laser might be to use a high powered UV-diode with focusing optics to make a small enough dot of light to be useful.

(READ WITH CARE) how dangerous is Ultraviolet light (UV) wavelength ?

Ultraviolet light (UV) is non-ionizing radiation in the 180 to 400-nanometer wavelength region of the electromagnetic spectrum. The ultraviolet spectrum is commonly divided into the following three regions:

UVA Black Light 315nm .. 400nm

UVB Erythemal 280nm .. 314nm

UVC Germicidal 180nm .. 280nm

Exposure to ultraviolet radiation is typically limited to the UVA region resulting from exposure to direct sunlight. The Earth’s atmosphere shields us from the more harmful UVC and greater than 99% of UVB radiation. However, some equipment can generate concentrated UV radiation in all the spectral regions that, if used without the appropriate shielding and personal protective equipment, can cause injury with only a few seconds of exposure.

EXPOSURE TO ULTRAVIOLET LIGHT

An unfortunate property of UV radiation is that there are no immediate warning symptoms to indicate overexposure. Symptoms of overexposure including varying degrees of erythema (sunburn) or photokeratitis (welder’s flash) typically appear hours after exposure has occurred.

Skin Injury - UV radiation can initiate a photochemical reaction called erythema within exposed skin. This “sunburn” can be quite severe and can occur as a result of only a few seconds exposure. Effects are exaggerated for skin photosensitized by agents such as coal tar products, certain foods (e.g., celery root), certain medications and photoallergens. Chronic skin exposure to UV radiation has been linked to premature skin aging, wrinkles and skin cancer.

Eye Injury – UV radiation exposure can injure the cornea, the outer protective coating of the eye. Photokeratitis is a painful inflammation of the eye caused by UV radiation-induced lesions on the cornea. Symptoms include a sensation of sand in the eye that may last up to two days. Chronic exposures to acute high-energy UV radiation can lead to the formation of cataracts.

SPECIAL WORK PRACTICES

first rule: never allow the skin or eyes to be exposed to UV radiation sources. The UV radiation generated by laser equipment can exceed

recommended exposure limits and cause injury with exposures as brief as three seconds in duration.

second rule to avoid Eye Injury: use protection glass, these are essential when operating a Class IV or Class IIIb laser in an environment where reflections can occur. They absorbs wavelengths from 370nm to 560nm, with an OD of +5 to +6 depending on the wavelength, unfortunately these will not provide protection against red or infrared lasers. They are intended for use with green, blue, and violet lasers.

405nm laser should be the safer choice

polygon mirror

Its assembly is mounted vertically on the flatbed scanners sled. The flatbed scanner sled is the Vertical axis, and the polygon mirror defelcting the laser in the scanner is the horizonbtal axis. Each Horizontal line is scanned about 150 times before the sled moves on to the next vertical position. The laser is scanned by the mirror continuasly at 55 Revolutions of the mirror per second, or 333 Hz scanrate, as the mirror is hexagon shaped. The exposure pattern is produced by turning the laser on and of synced to the rotation of the mirror.

Optics & Optical Issues

The original laser in a laserprinter is infrared, and that wavelength doesn't work for exposing pcbs which need 405nm at least.

You'd removed the infrared laser, and make a nice alluminium laser mount milling down the mirror assembly to fit it. As the lenses in the polygon mirror assembly had the wrong optical properties for my application, csudr different wavelength and different focussing distance, you'd removed them all.

The optical system should consists only of the laser, its focussing lens, and the polygon mirror.

There is one problem with this: as the beam length varies with the angle of the deflected laser beam, the focus of the laser lens would also have to be adjusted for each beam length. As this isn't done, the laser gets blurry at the ends and the middle of the scanline. But this is not a problem in practice, as the image gets sharp enough.